This invention relates to the monitoring of various operating conditions of a digital magnetic tape unit or tape recorder.
A digital magnetic tape unit magnetically stores or reads information or data bits along a plurality of parallel tracks on a magnetic recording tape to which motion is imparted by a tape transport mechanism at a predetermined, constant speed. Generally such tape units have seven or nine separate track channels along which information is fed from corresponding write heads mounted as an assembly aligned perpendicular to the direction of tape travel. Data bits are recorded along the parallel tracks on the tape for simultaneous pick-up by the read heads when properly aligned. The tape unit may be adjusted to establish read head alignment as well as to set the proper tape speed and adjust signal amplitude. It is essential that proper head alignment, tape speed and signal amplitude conditions be maintained during prolonged use of the tape unit to avoid signal error and other malfunctions, especially when the tape unit is interfaced with some computer systems.
Various speed and signal amplitude monitoring devices are available per se and could be incorporated in a tape unit with considerable modification thereof both electrically and structurally. Sophisticated circuit systems are also available to both detect time displacement between channel signals, referred to as "skew" and correct associated signal error as disclosed for example in U.S. Pat. Nos. 3,728,679 and 3,800,280 to McIntosh and Heffner, respectively. Such skew detection and error correction systems often malfunction or become ineffective and do not provide the user with any notice or indication of the situation. As to "skew" caused by read head misalignment, adjustment is usually made at the factory or during installation. Such skew adjustment is periodically checked since mechanical vibrations sometimes cause the head assembly to "skew".
It is therefore an important object of the present invention to provide a reliable and inexpensive monitoring system for magnetic tape units through which development of a skew condition will be indicated.
Yet another object is to provide the aforesaid monitoring system with means to indicate other operating conditions of the tape unit such as tape speed and signal amplitude, in a manner capable of being easily and readily interpreted by the user.